In recent years, a cold-cathode electron emission source has been applied to a field emission display or the like, and various forms such as an MIM type, an MIS type, a CNT type, a BSD type, a spindt type, and an SED type have been proposed (for example, refer to PTL 1). Various methods of creating a semiconductive layer that constitutes such an electron source have been proposed, and there is a method of applying resin solution, in which conductive particles are dispersed, as a simple creating process (for example, refer to PTL 2). Such a method has an advantage that it is possible to reduce costs of a manufacturing apparatus as an atmospheric process and an element is able to be created at a relatively low temperature by selecting resin.
FIG. 10 is a schematic structural view of a conventional electron emission element. In a conventional electron emission element 101, a semiconductive layer 104 serving as an electron acceleration layer is laminated on a substrate 102 having a first electrode, and a second electrode 105 serving as an electron emission surface is further formed on the semiconductive layer 104. Additionally, on the substrate 102, a region (insulating region RZ) where an insulating layer 103 with any pattern is formed is provided to be used for a wire 106 or the like. That is, a region exhibiting conductivity as an electron emission region RD by the semiconductive layer 104 directly contacting the substrate 102 and the insulating region RE are provided in the electron emission element 101. The electron emission element 101 includes a power supply 111 that is connected between the first electrode and the wire 106 and a ground power supply 112 that is connected between the first electrode and the power supply 111 and grounded. In the electron emission region RD of the electron emission element 101, irregularity may cause a case where an electric field is locally concentrated and insulation breakdown occurs or a case where an electron emission amount varies, so that it is important to manage a surface state.
The electron emission element 101 performs electron emission by applying voltage across the first electrode (surface of the substrate 102) and the second electrode 105, but at this time, current that flows through the element without contributing to electron emission is generated in some cases. Thus, it is desired that the insulating layer 103 that prevents electrons from flowing from the substrate 102 side is formed to suppress generation of unnecessary current in the element in a part (insulating region RZ) that is formed with the wire 106 or the like and does not involve in the electron emission. Moreover, in a case where a contact terminal or the like is brought into pressure contact with the wire 106 for power feeding, the insulating layer 103 preferably has a mechanically strong property so that no leakage current that flows to the substrate 102 through the wire 106, the second electrode 105, and the semiconductive layer 104 is generated.
As a method of forming the insulating layer 103, there are a method of forming a conductive thin film on an insulating region material such as glass, ceramic, or resin, a method of attaching an insulating sheet or the like onto a conductive substrate, and the like. For example, there is also a method that an aluminum substrate is anodized, an anodized film (hereinafter, also called an alumite film) in a region serving as an electron emission region RD is peeled off through etching or the like, and a conductor part is formed (for example, refer to PTL 3). This method has an advantage that the electron emission region RD and the insulating region RZ are able to be formed of the same material and manufacturing with relatively low costs is achieved, and additionally, the alumite film is excellent in insulating resistance and leakage resistance.